Vittorio Vittori

Design System Architect / Senior UX Designer

Single Source of Truth

A centralized repository where all design decisions live, ensuring consistency across all platforms, tools and teams.

Design Systems
Architecture

When I design a design system, I treat it as the single authoritative source for components, patterns, accessibility rules, and behavioral decisions.

This approach reduces ambiguity, subjective interpretation, and divergence between design and development.

In practice, I have consistently observed that when multiple "sources of truth" coexist—design files, local implementations, undocumented patterns—teams start to:

  • duplicate solutions,
  • rebuild components locally,
  • and make visual or technical decisions outside the system.

For this reason, anything that is not expressed within the design system should not be considered official. Every extension or change must pass through the system itself, in an explicit, documented, and versioned way.

The goal is not control, but clarity: enabling teams to trust the system and focus on product work rather than interpretation and reconciliation.

Tools like Storybook as a primary reference

In a production design system I worked on, Storybook was intentionally positioned as the operational source of truth, not as a secondary showcase.

Interactive documentation

Centralize components, variants, and states in a single, shared environment. Treat design files or screenshots as the primary authority. Use Storybook as a common reference for designers and developers. Consider documentation as something derived after implementation rather than part of the system itself.
A list of tools and services related to this argument. Interactive documentation
Storybook logoStorybook
it may be outdated

Components designed as public APIs

Components were defined as stable contracts rather than flexible local implementations.

Interactive documentation

Expose a limited and intentional set of properties. Expose internal implementation details for convenience. Document supported behaviors and constraints as part of the public API. Allow arbitrary overrides that introduce uncontrolled divergence.
A list of tools and services related to this argument. Type systems
TypeScript logoTypeScript
Documentation
Storybook logoStorybook
it may be outdated

CI/CD pipelines as alignment mechanisms

The build and deployment pipeline was used not only for distribution, but as a mechanism for enforcing coherence between design and development.

CI/CD pipeline stages

Automate validation and publishing processes. Rely on manual releases. Separate environments to make the actual state of the system explicit. Allow discrepancies between documented components and shipped code.
A list of tools and services related to this argument. CI/CD
GitHub logoGitHub Actions
Version management
Changeset logoChangesets
it may be outdated

Explicit processes for system changes

Design system evolution was handled through clearly defined and traceable processes.

Change proposal workflow

Provide official channels for proposing new features or changes. Accept informal or undocumented modifications. Make decisions visible and shared across disciplines. Prioritize urgency over long-term system integrity.
A list of tools and services related to this argument. Version control
GitHub logoGitHub
Issue tracking
GitHub logoGitHub Issues Linear logoLinear
it may be outdated

Accessibility embedded in the source of truth

Accessibility requirements were integrated directly into the design system rather than treated as external guidelines.

Accessibility integrated in components

Treat accessibility as a baseline requirement. Apply accessibility fixes downstream. Make constraints visible to both designers and developers. Separate accessibility rules from the components that implement them.
A list of tools and services related to this argument. Accessibility testing
Storybook logoStorybook A11y addon
Documentation
Storybook logoStorybook
it may be outdated

Why this principle matters

A single source of truth is not about enforcing rigidity.

It is about:

  • reducing decision noise,
  • increasing confidence in the system,
  • preventing the silent fragmentation that turns design systems into optional libraries.

Without this principle, a design system inevitably becomes:

  • a theoretical reference,
  • a partially adopted toolkit,
  • or a document that teams gradually ignore.
Single Source of Truth